Conductive polymers are being actively investigated because of their potential in production of inexpensive organic transistors. Conductive polymers have a structure in which a conjugated chain extends as a main chain, and show a high conductivity in such a direction. However, such conductive polymers are utilized in a bulk state because of the absence of an effective technology for orienting main chains of the conductive polymer, and sufficient electroconductivity is currently not obtained because the conduction between the polymer chains is achieved by the hopping conduction. For orienting the polymer chains, investigations are being conducted, for example, utilizing a Langmuir-Blodgett film.
A structured material prepared by using molecular assemblies of surfactants as a template has a structure in which molecular assemblies of the surfactant are regularly arranged by self-organization in a matrix of an inorganic compound. Particularly, a structured material having pores of an average diameter of 2 to 50 nm is called a mesoporous structure, which is referred to as a mesostructured material in the present description. A structured material in which pores are filled with a material is also called a mesostructured material. Initially, the inorganic compound was limited to silica, but such a structure can now be prepared with various materials such as oxides, metals or sulfides. A structure in which pore walls are constituted of an inorganic-organic nanocomposite material is now also available. Also, the originally found material was in a powder state, but now various forms, such as a film, a fiber, a sphere etc., are available.
The mesostructured material, by making it possible to introduce another material into regular nanospaces, thereby controlling structure or orientation of such material, is expected to be of use for applications in electronic materials and optical materials in addition to conventional applications of porous materials, such as an adsorption/separation material or a catalyst, and investigations are being conducted in a wide variety of fields. There are principally two methods for introducing a material into the pores of a mesostructure material. One is to eliminate the surfactant assemblies constituting pores and introduce a guest material into thus formed hollow pores. This method is generally employed for mesoporous silica, but cannot be applied to a material in which the mesostructure is damaged by the elimination of the surfactant assemblies. This method has a difficulty related to the introduction of a bulky guest species, such as a polymer material, when the structure is a film or the like. The other method is to make the guest species coexist during the preparation of a mesostructured material, whereby the guest species is held in the pores at the time the mesostructured material is prepared. This method has an advantage in that it is applicable to a wide range of mesostructure materials since the surfactant need not be eliminated, but there is a considerable limitation as to the guest species that can be introduced by this method.
There recently has been reported a technology of forming a functional material in pores by a method other than the two methods mentioned above. This method is based on providing the surfactant itself with a functionality and preparing a mesostructured material having a functional material in the pores without eliminating the surfactant. This method is applied to a film, or a fiber as described in Angewandte Chemie, International Edition, 40, pp. 3803-3806, in which a mesostructured material is prepared by using surfactants having a polymerizable functional group in the molecular structure and then polymerization is achieved by heat etc., thereby preparing conductive polymer chains in the pore.
However, the aforementioned method of preparing a mesostructured material utilizing surfactants having a polymerizable functional group in the molecular structure is difficult to practice because of the following reasons.
In a film employed in prior technologies, tubular pores in the film plane have random directions so that the polymer chains have random directions macroscopically even if a polymer chain is formed along the pore direction. On the other hand, a fibered structure is small and difficult to handle, and also, as described in Advanced Materials, 12, pp 961-965, a pore formed a spiral in the fiber. Consequently, even if the polymer chain is oriented along the direction of the pore, the polymer chain assumes a spiral form in this method so that it is difficult to control the direction of the polymer chain by the pores.
On the other hand, Science, 288, pp 652-656 describes a partial orientation of a conductive polymer compound utilizing a mesostructured silica monolith in which pore direction is oriented by a strong magnetic field. This method eliminates the surfactant by calcination after the preparation of a mesostructured silica and to introduce a conductive polymer compound into thus formed hollow nanospace, but the obtained mesostructured silica, having numberless fine cracks, is difficult to apply to an optical material or an electronic material, and an alignment control of conductive polymer main chains over the entire structure is not achieved as the polymers present in such cracks are random.
The present invention is to achieve an orientation control of polymer chains on a macroscopic scale, utilizing a mesostructured film in which tubular pores are oriented in one direction.